1. Technical Field
The present invention relates to a method and apparatus for registering wireless terminals with an access point through a wireless network. More particularly, the present invention relates to a method and apparatus for registering wireless terminals with an access point through a wireless network in which when an access point (hereinafter, referred to as “AP”) in a wireless local area network (WLAN) system is restarted, a restart situation is transmitted to the wireless terminals over a WLAN so as to allow the position registration of the wireless terminals to be easily performed, such that the AP provides a service to the terminals belonging to its service area on a stabilized basis.
2. Related Art
The term “WLAN” refers to building a network environment from a hub to respective terminals using wireless frequency or light in place of a wireless cable in an indoor or outdoor environment confined to a certain space or building such as office, downtown, home and the like. The WLAN involves a local area wireless communication technology using a wireless access protocol, such as IEEE 802.11, in an unlicensed frequency band of 2.4/5 GHz. The WLAN was originally developed as a substitute for a wired LAN cable, and has been so far used to build a small-scale wireless network environment primarily in enterprises. However, recently, the WLAN technology is being newly highlighted as a public network technology that provides broadband wireless Internet access service to service subscribers out of an original limitation of being evolved from the wired LAN technology.
The WLAN is composed of a collection of stations called Basic Service Sets (BSSs). Basically, the term “BSS” encompasses both an independent BSS and an infrastructure BSS. In this regard, a “station” is an entity for making a connection using a wireless medium. An example of a station includes a Network Interface Card (NIC) mounted on a personal computer (PC) or a notebook computer.
In the independent BSS, communication between stations is made over a limited distance without using an access point (AP). That is, communication between terminals is accomplished by building an ad hoc network in a state where the terminals are not connected to a wired network, such as a LAN. In the WLAN, information as to how the terminals discover each other, how the terminals synchronize with a timer, and how the terminals maintain battery power is provided.
The infrastructure BSS involves a structure in which each BSS includes one AP connected to the wired network. The AP registers a terminal with the BSS, authenticates the terminal, and performs processing on roaming and mobility of a station. Further, the AP includes additional functions, such as firewall, NATs, DHCP server/client, VPN, and the like.
In the BSS mode, the AP serves as a connection point with respect to the wired network. Under a general premise environment, only one AP is present for several terminals. Since the 802.11 standard supports Intra-BSS mobility, the wireless terminal can accept the same service regardless of its position only if the wireless terminal moves within the AP area.
Further, several BSSs connected by a backbone network can cover a more extended area. Such a backbone network, connected with the BSSs, is called a Distributed System (DS). In this regard, the respective BSSs are discriminated by a 48-bit BSS identifier (ID) which is similar to a MAC address in the 802.3 type LAN. Building the distributed system at places such as a campus or a conference center can provide WLAN service in a broader area.
When the wireless terminals roam from one BSS to another BSS, the DS allows a user to freely roam and receive a packet at a new position. Although the DS may be configured for any form of network, it generally uses an 802.3 type LAN. A form in which two or more BSSs are connected to the DS so as to build one sub-network is called an Extended Service Set (ESS).
Respective ESSs are discriminated by an ESS ID. Wireless terminals always belong to a particular BSS and ESS. When the wireless terminals move from one BSS (BSS-A) to another BSS (BSS-B), both of which belong to the same ESS, packets must be properly routed to the moving terminals. The APs in the respective BSS-A and BSS-B are responsible for the routing function. The APs route the packets to other terminals in the BSS or in another BSS in the same ESS. The wireless terminal may include a note PC, a smart card, a VoIP phone, or the like, capable of performing WLAN voice/data communication.
As a result, the APs are entities that connect between a wireless medium and a wired network, such as an 802.3 type network. The AP becomes a base station for a WLAN device, and serves to connect the device with a wired network, such as a LAN.
In this WLAN system, the APs will perform a restart when power is down, when a network interface card (NIC) stage is dead due to network traffic loads, other attacks or the like, or when a bug exists in software. When the APs are restarted, an entire address resolution protocol (ARP) table for all wireless terminals registered in the service area of the APs is cleared. Accordingly, the APs cannot recognize which of the terminals are currently registered with the APs because the media access control (MAC) list of the wireless terminals reserved by the APs is deleted when the APs are restarted. In addition, because the terminals do not recognize that the APs have performed the restart, a situation such as a connection failure or the like will arise.
The ARP table for the wireless terminals registered with the AP will be described briefly.
The address resolution protocol (ARP) is a protocol used when the AP desires to know the MAC address of a wireless terminal in the situation wherein the AP is aware of an IP address of the wireless terminal. Conversely, a reverse ARP (RARP) is a protocol used when the AP desires to know an IP address using the MAC address of the wireless terminal.
A process of determining a MAC address using an ARP will be described briefly. The MAC address of a wireless terminal is needed in order to communicate with the wireless terminal in a WLAN interval.
The MAC address has a unique value of 6 bytes per each NIC (i.e., LAN card). To determine the MAC address, the AP transmits an ARP packet containing the IP address of the wireless terminal to the wireless terminal over the WLAN in a broadcast communication in a manner distinguishable from the prior art
Each NIC of each wireless terminal connected to the WLAN receives this packet, and causes a central processing unit (CPU) in the terminal to analyze the packet. The NIC compares the IP address in the packet to its IP address. If the two addresses do not match, the NIC ignores the packet; if two addresses do match, the NIC transmits the packet containing the MAC address of the NIC to the AP.
Using the MAC address of the wireless terminals determined through such a process, the AP transmits a packet having desired data containing the address to perform unicast communication.
Furthermore, the AP periodically sends beacon data to the wireless terminal. Because a note-PC, a general desktop PC, or the like is not influenced by power consumption as a result of using a large capacity battery, the PC sets up a link to the AP suitable for a relevant area using periodically received beacon data to accomplish resuming of the link until the link to the AP is re-established after the link to the AP is dropped. At this time, the PC of course must use a mechanism in which the ARP is reconfigured by resetting its relevant information.
However, in contrast to the above case, due to power consumption considerations, the voice wireless terminal is not permitted to have a polling structure by means of which the periodically received beacon is checked. Attempting polling when a link is dropped causes power consumption several times greater than the power consumption in a normal standby mode, and this greatly influences standby mode time.
Substantially, there is a frequent occurrence of the case wherein the voice wireless terminal cannot reset itself due to a difference in a scanning time or the like, and this is in contrast to a data terminal such as a note-PC or the like. Accordingly, the AP is not obligated to process signaling for a terminal in which resumed setup is not carried out, and the AP cannot confirm whether the relevant voice wireless terminal belongs to the AP.
As a result, conventionally, when the AP is restarted, the MAC list for all wireless terminals is initialized. Accordingly, even though a wireless terminal transmits signaling, the AP cannot recognize it. The reason is that the ARP table in the AP can perform signal processing only for terminals registered with the AP.
Furthermore, there are problems in that the wireless terminal cannot at all recognize whether the AP has performed a restart, and the AP cannot confirm whether there are wireless terminals connected to the AP, which causes connection failure or the like.
The following patents are considered to be generally pertinent to the present invention, but are burdened by the disadvantages set forth above: U.S. Pat. No. 6,680,922 to Jorgensen, entitled METHOD FOR THE RECOGNITION AND OPERATION OF VIRTUAL PRIVATE NETWORKS (VPNS) OVER A WIRELESS POINT TO MULTI-POINT (PTMP) TRANSMISSION SYSTEM, issued on Jan. 20, 2004; U.S. Pat. No. 6,594,246 to Jorgensen, entitled IP-FLOW IDENTIFICATION IN A WIRELESS POINT TO MULTI-POINT TRANSMISSION SYSTEM, issued on Jul. 15, 2003; U.S. Pat. No. 6,452,915 to Jorgensen, entitled IP-FLOW CLASSIFICATION IN A WIRELESS POINT TO MULTI-POINT (PTMP) TRANSMISSION SYSTEM, issued on Sep. 17, 2002; U.S. Pat. No. 6,058,106 to Cudak et al., entitled NETWORK PROTOCOL METHOD, ACCESS POINT DEVICE AND PERIPHERAL DEVICES FOR PROVIDING FOR AN EFFICIENT CENTRALLY COORDINATED PEER-TO-PEER WIRELESS COMMUNICATIONS NETWORK, issued on May 2, 2000; U.S. Pat. No. 6,535,493 to Lee et al., entitled MOBILE INTERNET COMMUNICATION PROTOCOL, issued on Mar. 18, 2003; U.S. Pat. No. 6,073,016 to Hulthen et al., entitled MOBILE DEVICE ID ALLOCATION SYSTEM AND METHOD, issued on Jun. 6, 2000; U.S. Pat. No. 6,717,926 to Deboille et al., entitled APPARATUS AND ASSOCIATED METHOD, BY WHICH TO TRANSMIT BEACON SIGNALS IN A RADIO COMMUNICATION SYSTEM, issued on Apr. 6, 2004; U.S. Pat. No. 6,201,811 to Larsson et al., entitled TRANSFERRING IDENTIFIER INFORMATION IN A TELECOMMUNICATION SYSTEM, issued on Mar. 13, 2001; U.S. Pat. No. 5,991,287 to Diepstraten et al., entitled SYSTEM AND METHOD FOR PROVIDING SEAMLESS HANDOVER IN A WIRELESS COMPUTER NETWORK, issued on Nov. 23, 1999; U.S. Pat. No. 5,724,346 to Kobayashi et al., entitled MEANS FOR MAINTAINING CONNECTABLE ACCESS POINTS OWING TO MOVEMENT OF A MOBILE STATION BETWEEN CELLS IN A WIRELESS LAN SYSTEM, issued on Mar. 3, 1998; U.S. Pat. No. 6,681,259 to Lemilainen et al., entitled METHOD FOR COUPLING A WIRELESS TERMINAL TO A DATA TRANSMISSION NETWORK AND A WIRELESS TERMINAL, issued on Jan. 20, 2004; and U.S. Pat. No. 6,067,297 to Beach, entitled EMBEDDED ACCESS POINT SUPPORTING COMMUNICATION WITH MOBILE UNIT OPERATING IN POWER-SAVING MODE, issued on May 23, 2000.